Given three strings ‘str’, ‘oldW’ and ‘newW’. The task is find all occurrences of the word ‘oldW’ and replace then with word ‘newW’. Examples:
Input : str[] = "xxforxx xx for xx",
oldW[] = "xx",
newW[] = "neveropen"
Output : neveropen neveropen for neveropen
The idea is to traverse the original string and count the number of times old word occurs in the string. Now make a new string of sufficient size so that new word can be replaced. Now copy original string to new string with replacement of word.
Implementation:
C
// C program to search and replace // all occurrences of a word with // other word. #include <stdio.h> #include <stdlib.h> #include <string.h> // Function to replace a string with another // string char* replaceWord(const char* s, const char* oldW, const char* newW) { char* result; int i, cnt = 0; int newWlen = strlen(newW); int oldWlen = strlen(oldW); // Counting the number of times old word // occur in the string for (i = 0; s[i] != '\0'; i++) { if (strstr(&s[i], oldW) == &s[i]) { cnt++; // Jumping to index after the old word. i += oldWlen - 1; } } // Making new string of enough length result = (char*)malloc(i + cnt * (newWlen - oldWlen) + 1); i = 0; while (*s) { // compare the substring with the result if (strstr(s, oldW) == s) { strcpy(&result[i], newW); i += newWlen; s += oldWlen; } else result[i++] = *s++; } result[i] = '\0'; return result; } // Driver Program int main() { char str[] = "xxforxx xx for xx"; char c[] = "xx"; char d[] = "Geeks"; char* result = NULL; // oldW string printf("Old string: %s\n", str); result = replaceWord(str, c, d); printf("New String: %s\n", result); free(result); return 0; } |
Output:
Old string: xxforxx xx for xx New String: neveropen Geeks for Geeks
Time Complexity: O(n)
Auxiliary Space: O(n)
Method 2: This method involves the in-place update of the string. It is more efficient as it uses only extra space for the new characters to be inserted.
Implementation:
C
// C Program to replace a word in a text by another given// word by inplace updation#include <stdio.h>#include <stdlib.h>#include <string.h>void replaceWord(char* str, char* oldWord, char* newWord){ char *pos, temp[1000]; int index = 0; int owlen; owlen = strlen(oldWord); // Repeat This loop until all occurrences are replaced. while ((pos = strstr(str, oldWord)) != NULL) { // Bakup current line strcpy(temp, str); // Index of current found word index = pos - str; // Terminate str after word found index str[index] = '\0'; // Concatenate str with new word strcat(str, newWord); // Concatenate str with remaining words after // oldword found index. strcat(str, temp + index + owlen); }}int main(){ char str[1000], oldWord[100], newWord[100]; printf("Enter the string: "); gets(str); printf("Enter the word to be replaced: "); gets(oldWord); printf("Replace with: "); gets(newWord); replaceWord(str, oldWord, newWord); printf("\nModified string: %s", str); return 0;} |
Input:
1 xxforxx xx for xx xx neveropen
Output:
neveropen neveropen for neveropen
Time Complexity: O(n)
Auxiliary Space: O(1)
Feeling lost in the world of random DSA topics, wasting time without progress? It’s time for a change! Join our DSA course, where we’ll guide you on an exciting journey to master DSA efficiently and on schedule.
Ready to dive in? Explore our Free Demo Content and join our DSA course, trusted by over 100,000 neveropen!
Ready to dive in? Explore our Free Demo Content and join our DSA course, trusted by over 100,000 neveropen!
